Semipermeable filtration membranes are useful in many situations where a liquid must be purified. These membranes are constructed to be selective in their permeability. They allow certain molecules or ions to pass through them by diffusion but other molecules or ions are not allowed to pass.
One problem often encountered with filtration membranes is that after a given period of time, fouling and clogging may prevent the filtration membranes from operating efficiently. This is generally caused by relatively large organic molecules present in the liquid to be purified, for instance contaminated water. These molecules gradually form a biofilm, which biofilm can be generally defined as an undesirable accumulation of waterborne microorganisms and contaminants on the active surface of a filtration membrane. The active surface of a filtration membrane often creates a proper environment for the growth of these microorganisms. Over time, the biofilm can clog the pores of the filtration membrane. Frequent maintenance interventions are often needed as a result of this problem. This adds costs and complexity.
In some implementations, it can also be desirable to remove some of the dissolved gases from liquids going through filtration membranes. Examples of such dissolved gases are ammonia, hydrogen sulfide, volatile organic compounds (VOCs), volatile by-products of dissolved organic carbon (DOC) degradation and/or other low boiling point vapors contaminants. These gases can be present in liquids to be purified and may downgrade the quality of the purified liquids. Removing these dissolved gases, at least partially, is thus often desirable.
Clearly, there is still room for improvements in this area of technology.